Frequency mixers, or mixers, may be used in radio frequency (RF) communication systems to shift a center frequency of a data signal for more convenient processing of the data signal. Mixers may be active or passive devices. A conventional active mixer may employ a Gilbert cell.
A gain of a conventional active mixer employing a Gilbert cell may be sensitive to temperature variation. A conventional technique may compensate for temperature variation by making a common-mode voltage of baseband input transistors temperature dependent. However, this technique has a drawback that the input transistors may deviate from behaving as an ideal current source, especially at higher temperatures, which may degrade linearity of the mixer. There is thus a need to improve the linearity of active mixers employing Gilbert cells, especially as operating temperature increases.